System and method for handling power state change requests initiated by peripheral devices

Abstract

A computer operating system is coupled to intelligent peripheral devices via a peripheral bus architecture that supports unsolicited status requests from peripheral devices. Each peripheral device has local power management that initiates an unsolicited power change request when the device is preparing to change power states. The peripheral bus carries the unsolicited power change request to the operating system. Upon receipt, the operating system issues a power change request directing the peripheral device to perform the power state transition. In this manner, the operating system remains aware of the peripheral device's power state and acts as if it is controlling the device's power state transitions.

What is claimed is:  
     
       1. In a system comprising a host device coupled across an external bus to a peripheral device having local power management, a method for managing a power state transition in the peripheral device, the method comprising: 
       receiving a status message from the peripheral device indicating that the local power management, independent of any power management policy implemented at the host device, will perform an upcoming power state transition from a first power state to a second power state;  
       in response to receiving the status message, generating a status received message indicating that the host device is aware that the local power management is placing the peripheral device into the second power state; and  
       sending the status received message to the peripheral device.  
     
     
       2. A method as recited in  claim 1 , further comprising the host device performing an operation involving the peripheral device before sending the status received message . 
     
     
       3. A method as recited in  claim 1 , further comprising the host sending a request to the peripheral device before sending the status received message. 
     
     
       4. An operating system stored on a computer-readable storage medium, the operating system comprising computer-executable instructions for: 
       receiving a status message from a peripheral device over a peripheral bus that is external to a host device controlled by the operating system, the status message informing the operating system that local power management of the peripheral device, independent of any power management policy implemented at the host device, will perform an upcoming power state transition from one power state to another power state;  
       responsive to receiving the status message, generating a status received message indicating that the host device is aware that the local power management is placing or is going to place the peripheral device into the other power state; and  
       sending the status received message over the peripheral bus to the peripheral device.  
     
     
       5. An operating system as recited in  claim 4 , further comprising computer-executable instructions for performing an operation involving the peripheral device before sending the status received message. 
     
     
       6. An operating system as recited in  claim 4 , further comprising computer-executable instructions for sending a request to the peripheral device before sending the status received message. 
     
     
       7. In a system comprising a computer coupled across an external peripheral bus to a peripheral device, the computer comprising a processor operatively coupled to a memory, the computer comprising: 
       an operating system stored in the memory and executable on the processor, wherein the peripheral device comprises local power management configured to manage transition of the peripheral device between first and second power states, the local power management being capable of communicating an unsolicited status message indicating that local power management of the peripheral device will perform a power state transition between the first and second power states, the power state transition being independent of any power management policy implemented by the operating system; and  
       the operating system being configured to receive the unsolicited status message from the peripheral device over the external peripheral bus and in response, to issue a status received message indicating that the operating system is aware that the local power management is placing, or is going to place, the peripheral device into the other power state.  
     
     
       8. A computer as recited in  claim 7 , wherein the operating system is further configured to perform an operation involving the peripheral device before issuing the status received message. 
     
     
       9. A computer as recited in  claim 7 , wherein the operating system is further configured to send one or more requests to the peripheral device before issuing the status received message.